Such landing gears of the tripod type are already known to the prior art. These landing gears consist essentially of a leg of which one end is fixed at a first point of the aircraft; a shock absorber of which end is fixed at a second point of the aircraft different from the first, and a strut of which one end is fixed at a third point of the aircraft, evidently different from the other two. These three elements are then connected substantially on their other ends at the same fourth point to form a trihedral whose apex is turned downward when the aircraft is rolling on the ground. This apex or fourth point supports the traveling means, for example, one or more wheels. This design in the form of a trihedral which is inverted when the landing gear is extended has given rise to the name "tripod landing gears" well known to aeronautical technicians. These fixing points mentioned above are given only as a general indication of a fixing location and, in practice, these "points" consist of cardan joints, knuckle joints, pins, etc., which are defined according to landing gear design rules to ensure traveling, shock absorption and the movement of the landing gear from one position to another, i.e. the retracted and extended positions.
Among landing gears of this tripod type, there is one which makes it possible to pivot the wheel by about 90 degrees when the landing gear moves from one of the two positions to the other as defined above. This rotation of the wheel allows the landing gear, when it is retracted into its well in the fuselage, to occupy a smaller volume and hence to be housed more easily.
This rotation of the wheel is obtained by means of a so-called tripod landing gear structure in which the end of the strut connected to the leg at the fourth point defined above comprises a rotary ring around the leg and two rotary links turning in relation to each other around the same axis at one of their ends, the two other respective ends of the two links being connected to the strut and to a pin supporting the aircraft wheel and capable of pivoting in a bearing provided for this purpose in the leg.
With this configuration, when the landing gear goes from one position to the other, the strut undergoes a rotation which causes a rotation of the wheel with the same amplitude thanks to the pivoting ring mounted around the wheel.
This type of embodiment gives the desired results, i.e. pivoting of the wheel when the landing gear goes from one position to the other, but the above description of the structure of this landing gear shows that it is relatively complicated.
It is the object of the present invention to provide a retractable landing gear of the tripod type allowing a rotation through a certain angle of the rolling means, i.e. a wheel in the most current cases, when the landing gear goes from one position to the other, l.e. moves between the retracted and extended positions, so that when the landing gear is extended the plane of the wheel is parallel to the axis of the aircraft and, when the landing gear is retracted, the plane of this wheel has undergone a rotation in relation to the leg which supports it and so that, for example, this wheel plane always remains parallel to the axis of the aircraft. More precisely, it is the object of the present invention to provide a landing gear having the simplest structure while minimizing the number of its components compared with those of the prior art, particularly to secure an improvement in the reliability of these types of landing gear.
The present invention accordingly provides retractable landing gear of the tripod type for a rigid-frame aircraft, comprising:
a leg capable of being connected on a first end at a first fixed point of the aircraft frame via a first cardan joint to two, first and second, pins, said leg being mounted rotatably around the second pin, the other end of said leg supporting a pivoting pin on which can be mounted a rolling means, PA1 a shock absorber of which one end can be connected at a second fixed point of said frame via a second cardan joint to two, third and fourth, pins, said shock absorber being mounted rotatably around the fourth pin, the other end of said shock absorber being connected at a point of said leg around a fifth pin, this point being located near the aforesaid pivoting pin, PA1 a strut of which one end is capable of being connected at a third fixed point of said frame via a third cardan joint to two, sixth and seventh, pins, said strut being mounted rotatably around the seventh pin, the other end of said strut being connected to said leg through an eighth pin substantially near said pivoting pin, said strut being made up of at least two levers pivoting in relation to each other around a ninth pin, PA1 connection means between the end of said strut cooperating with the eighth pin and said pivoting pin supporting the rolling means, and PA1 means for controlling the alignment of the two levers of said strut, the said first, third, seventh, eighth and ninth pins being parallel in one direction whereas the second, fourth, fifth and sixth pins are parallel in a second direction, these two directions forming a non-zero angle between them.
According to one feature of the invention, the two said directions are perpendicular.
According to another feature of the present invention, the connection means between the end of said strut cooperating with the eighth pin and said pivoting pin supporting the rolling means comprise a link whose two ends are connected via knuckle joints with two stems respectively integral with said strut and with said pivoting pin so as to form two rotating moments respectively in relation to said eighth pin and to said pivoting pin.
According to a further feature of the present invention, said first and third pins are colinear.
According to yet another feature of the invention, the second and sixth pins are colinear.
Other characteristics and advantages of the present invention will appear from the following description given as an illustration in connection with the appended drawing representing a perspective view of an embodiment of a retractable landing gear of the tripod type according to the invention.